Inflatable occupant restraint system

ABSTRACT

A pressure vessel containing compressed fluid has the outlet thereof sealed by a rupturable plug. The outlet communicates with a manifold which in turn communicates with one end of an elongated cylindrical diffuser. The diffuser includes longitudinal rows of partial circumferential slots. Each row communicates the diffuser with the interior of a respective inflatable occupant restraint cushion. A cylinder is supported within the manifold by radial ribs thereof engaging the interior wall of the manifold. A conical headed piston is slidable within the cylinder and the space between the piston and a closed end wall of the cylinder is filled with viscous fluid. An aperture in the closed end wall of the cylinder receives a pintle secured to the piston. The conical head of the piston is located in predetermined relationship to a fixed area orifice at the outlet of the pressure vessel. A tubular diffuser screen is inserted within the diffuser and covers the slots to the cushions. One end of the screen opens to the manifold and the other end of the screen is closed by a plug of resilient material.

United States Patent Magyar [4 1 May 30,1972

[54] INFLATABLE OCCUPANT RESTRAINT SYSTEM [72] Inventor: Joseph J. Magyar, Rochester, Mich.

[58] Field of Search ..280/150 AB; 137/38, 68, 514.5;

[56] References Cited UNITED STATES PATENTS 2,339,101 1/1944 Parker ..l37/5l4.5 2,834,609 5/1958 Bertrand... 280/150 AB 3,105,506 /1963 Beeby ..l37/38 3,197,234 7/1965 Bertrand... 280/150 AB 3,527,472 9/1970 Chute et a1. ...280/l AB 3,561,561 2/1971 Trainor ..181/ X 3,602,527 8/1971 Goetz ..280/ AB Primary E.xaminerl(enneth H. Betts Attorney-W. E. Finken and Herbert F urman [5 7] ABSTRACT A pressure vessel containing compressed fluid has the outlet thereof sealed by a rupturable plug. The outlet communicates with a manifold which in turn communicates with one end of an elongated cylindrical diffuser. The diffuser includes lon gitudinal rows of partial circumferential slots. Each row communicates the diffuser with the interior of a respective inflatable occupant restraint cushion. A cylinder is supported within the manifold by radial ribs thereof engaging the interior wall of the manifold. A conical headed piston is slidable within the cylinder and the space between the piston and a closed end wall of the cylinder is filled with viscous fluid. An aperture in the closed end wall of the cylinder receives a pintle secured to the piston. The conical head of the piston is located in predetermined relationship to a fixed area orifice at the outlet of the pressure vessel. A tubular diffuser screen is inserted within the diffuser and covers the slots to the cushions. One end of the screen opens to the manifold and the other end of the screen is closed by a plug of resilient material.

4 Claims, 2 Drawing Figures INFLATABLE OCCUPANT RESTRAINT SYSTEM This invention relates generally to a vehicle body occupant restraint system and more particularly to a noise attenuation system for attenuating the noise created upon inflation of an inflatable occupant restraint cushion.

Occupant restraint systems conventionally include a vessel having an outlet sealed by a rupturable diaphragm or wall to contain the contents of the vessel therewithin until such time as the diaphragm or wall is ruptured either mechanically by the use of squibs or detonators, or otherwise. The sealed outlet of the vessel communicates with a manifold which in turn communicates with one end of a cylindrical difiuser. The other end of the diffuser is closed and the body of the diffuser is provided with one or more longitudinal rows of axially spaced partially circumferentially extending slots. Each row communicates the diffuser with the interior of a respective inflatable occupant restraint cushion.

The vessel may contain air or nitrogen under pressures in the order of 3,500 psi. Alternatively, the vessel may contain air at a lower pressure in combination with pyrotechnic gas generating material, or may contain only pyrotechnic gas generating material.

When the diaphragm or wall is ruptured, the column of air or other pressure fluid passing through the outlet of the vessel creates a supersonic high amplitude shock wave which is followed in a few milliseconds by a sonic high amplitude pressure front which is the column of pressure fluid. The shock wave and pressure front create high noise levels, such as 172 decibels.

Copending application Ser. No. 85,490 Prachar, filed Oct. 30, 1970 and assigned to the assignee of this invention, discloses a flow control device for controlling the rate of inflation of a vehicle body occupant restraint cushion and lowering the noise level upon inflation of the cushion. The flow control device generally includes a piston support within a cylinder in a predetermined position by viscous fluid contained between a closed end wall of the cylinder and one end of the piston. The other end of the piston is provided with a conically shaped head which is located in predetermined relationship to a fixed area orifice at the outlet of a pressure vessel to reduce the fixed area orifice to a lower or reduced effective area orifice. A pintle of predetermined shape secured to the one end of the piston extends in predetermined dimensional relationship to the wall of an aperture through the closed end wall of the cylinder. When the supersonic high amplitude shock wave engages or hits the head of the piston upon rupture of the wall sealing the pressure vessel outlets, the wave is immediately broken up and reshaped into a shock wave of lower amplitude. The subsequent air column pressure front is temporarily slowed as it passes through the orifice of reduced area. However, the force or pressure of such front gradually moves the piston within the cylinder as the viscous material is extruded from between the pintle and the wall of the aperture so that the effective area of the orifice is gradually increased. As the effective area of the orifice increases, the volume of pressure fluid and the pressure front increase, but at a rate much slower than the initial rate. This provides a generally uniform mean flow rate through the orifice to the inflatable cushion and likewise attenuates part of the noise created by the pressure front. Tests have shown that an occupant restraint system with such a flow control device can reduce the noise level by 4 to 6 decibels.

It is also known to provide a mufiler for compressed air systems which generally comprises a hollow cylinder having openings through the wall thereof, with the cylinder being pro vided with an internal tubular diffuser screen across the openings. The tubular diffuser screen may have up to eight layers of fine mesh screen across the openings of the cylinder. These layers are provided by rolling a sheet of screen material upon itself. One end of the tubular diffuser screen is open to the compressed air source and the other end is closed by a plug of resilient material such as rubber.

This invention combines a flow control device with a diffuser screen within the diffuser to obtain a noise attenuation system which reduces the noise levels in an inflatable occupant restraint system to much lower values than described hereinbefore. In the preferred embodiment of the invention, the flow control device disclosed in the Prachar application is provided in the manifold of the inflatable occupant restraint system, and the diffuser of such system is provided with a tubular diffuser screen across the openings of the diffuser to the inflatable cushion. Additionally the closed end of the diffuser or the diffuser screen is provided with a resilient plug.

If a restraint system is tested with only the tubular difluser screen in the diffuser, the decibel reduction obtained over a restraint system without the tubular diffuser screen is from one to six decibels. As pointed out earlier, if a restraint system is tested only with the flow control device, the decibel reduction obtained is from 4 to 6 decibels over a system without such a device. When a restraint system is tested with both the tubular screen and the flow control device, the resultant reduction obtained over a system without either is not merely additive of the individual reductions but much greater. A synergistic effect results since the resultant reduction obtained in a system with both is up to l5 decibels. At the decibel levels in question, approximately 172 decibels, such a resultant reduction results in an even greater decrease in the sound pressure level.

It is therefore the primary object of this invention to provide an improved noise attenuation system for a vehicle body occupant restraint system which includes a flow control device located adjacent the outlet of the pressure fluid source and providing a variable area orifice through which the pressure fluid must flow to a diffuser for the inflatable cushion, and also includes in combination therewith, a layer of porous material providing a tortuous path through which the pressure fluid must flow in order to pass from the diffuser to the inflatable cushion. v

This and other objects of the invention will be readily apparent from the following specification and drawings wherein:

FIG. 1 is a partially broken away partial perspective view of a portion of an occupant restraint system embodying a noise attenuation system according to this invention; and

FIG. 2 is a partial exploded view of a portion of FIG. 1.

Referring now to the drawings, FIG. 1 shows a portion of a conventional inflatable occupant restraint system designated generally 10. Such a system includes a pressure vessel 12 which may contain air or nitrogen under a pressure of up to 3,500 psi. The neck 14 of the vessel provides an outlet in which is threaded a plug and squib assembly 16. The assembly 16 generally includes a hollow cylindrical housing. The internal cylindrical bore of the housing receives a pair of electrically fired conventional squibs which are connected with a conventional sensor and a source of power, not shown. When an acceleration pulse of predetermined amplitude and time is sensed by the sensor, the squibs are fired by the source of power and the metal wall or plug 18 of the assembly 16 is ruptured to release the contents of the vessel 12 for inflation of an occupant restraint cushion.

The internal bore of the cylindrical housing of assembly 16 connects to a tubular manifold 20 which in turn connects to an elongated tubular diffuser 22. Contained within the manifold 20 is a flow control device designated generally 24 which is the same as that disclosed in detail in copending application Ser. No. 85,490 Prachar, filed Oct. 30, 1970, and assigned to the assignee of this invention. Accordingly, only a brief description of this device will be given herein, and reference may be had to the Prachar application for a description in detail. Generally, the device 24 includes a cylinder 26 which slidably supports a piston 28. The cylinder 26 is supported within the manifold 20 by three radial ribs which engage the inner surface of the manifold wall. The space 30 between the one end of the piston and the closed end wall of the cylinder 26 is filled with viscous material. A pintle 32 extends from the one end of the piston through an aperture in the closed end wall of the cylinder, with a predetermined dimensional relationship being set between the outer surface of the pintle and the wall of such aperture. The other end of the piston 28 is provided with a conical head 34. As shown, this head is located in a predetermined relationship to the outlet or orifice 36 of the internal bore of the housing of assembly 16. The conical head 34 restricts fluid flow through the outlet 36 by reducing the effective area of such outlet.

The diffuser 22 includes two longitudinal rows of partial circumferential openings or slots 38 and 40 which respectively communicate the interior of the diffuser with a torso cushion 42 and a knee cushion 44 for inflation of these cushions when the pressure fluid is released from the vessel 12. The details of the manner in which the cushions are inflated from their respective openings are not shown herein. Reference may be had to copending application Ser. No. 11,189 Cole, filed Feb. 13, 1970, and assigned to the assignee of this invention, for these details. The knee and torso cushions and the diffuser 22 are provided with a protective housing or covering 46 which splits when the cushions are inflated.

A tubular diffuser screen 48 fim within the difi'user 22. The difi user screen may extend for the full length of the diffuser 22 or otherwise, but it is important in accordance with this invent'ion that the screen cover the openings 38 and 40 to provide a tortuous flow path for the pressure fluid flowing through such openings. The diffuser screen 48 is made by rolling a sheet of fine mesh material, such as fine mesh metal screening, upon itself so that approximately eight layers of material are provided across each of the openings 38 and 40. The end of the tubular screen 48 remote from the manifold is closed by a plug 50 of resilient material, such as rubber. Normally the plug 50 will rest against the closed end wall, not shown, of the difiuser 22. Alternatively, such a plug may be provided in place of the end wall of the diffuser.

When the wall 18 is ruptured, the pressure fluid contents of the vessel 12 will flow through the internal bore of the assembly 16 through the flow control device 24 and into the interior of the diffuser screen 48. The pressure fluid will then flow through such screen and then through the openings 38 and 40 into the cushions 42 and 44 to inflate such cushions.

Upon initial rupture of the wall 18, the column of pressure fluid passing through the outlet 36 creates a supersonic high amplitude shock wave which is followed in a few milliseconds by a sonic high amplitude pressure front which is the column of pressure fluid. When the shock wave hits the conical head 34 of the piston 26, the wave is broken up and reshaped into a wave of lower amplitude. The air column pressure front is, of course, temporarily slowed by the reduced area orifice defined by the outlet 36 and the conical head 34 of the piston 28. However, the force or pressure of such front gradually moves the piston 28 within the cylinder 26 as the viscous material in space 30 extrudes outwardly of the cylinder from between the pintle 32 and the wall of the aperture in the closed end wall of the cylinder. Thus, the effective area of the orifice between outlet 36 and the piston head 34 increases and in turn the volume of pressure fluid and the pressure front increase but at a rate much slower than the initial flow rate. Thus, a generally uniform mean flow rate through the outlet 36 is obtained and part of the noise created by the pressure from is attenuated.

The pressure front is further attenuated by the tortuous flow path provided by the tubular diffuser screen 48, and likewise the shock wave is additionally attenuated by the plug 50. The overall decibel reduction obtained, as pointed out hereinbefore, is not merely additive but is greater so that a synergistic effect is obtained through both the use of the flow control device 24 and the diffuser screen 48.

While a tubular difluser screen is shown as being made from a rolled-up sheet of fine mesh screen material, it is believed obvious that such screen provides a layer or thickness of porous material across the openings of the diffuser. Accordingly, the tubular screen may be replaced by other materials lprroviding such a porous layer or thickness.

us, this invention provides an improved occupant restraint system.

I claim:

I. In an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, a manifold communicating with the outlet, an elongated annular diffuser communicating at one end thereof with the manifold and including a plurality of openings communicating the difliiser with an inflatable occupant restraint cushion, variable area orifice means within the manifold, means for increasing the efi'ective orifice area of the variable orifice means as a function of time after rupture of the seal, a layer of porous material positioned across the openings of the diffuser, and resilient means within the diffuser engageable by the pressure fluid flow adjacent the other end thereof.

2. In an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, a manifold communicating with the outlet, an elongated annular diffuser communicating at one end thereof with the manifold and including a plurality of axially spaced circumferentially extending openings communicating the diffuser with an inflatable occupant restraint cushion, variable area orifice means within the manifold, means for increasing the effective orifice area of the variable orifice means as a function of time after rupture of the seal, means within the diffuser providing an elongated layer of porous material covering the openings of the diffuser, and resilient means within the diffuser engageable by the pressure fluid flow downstream of the openings.

3. In an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, passage means communicating the outlet with an elongated hollow diffuser, variable area orifice means within the passage means receiving pressure fluid flowing through the outlet, means for increasing the effective orifice area of the variable orifice means as a function of time after rupture of the seal, means communicating the interior of the diffuser with an inflatable occupant restraint cushion and providing a tortuous pressure fluid flow path thereto, and resilient means within the diffuser engageable by the pressure fluid flow downstream of the communicating means.

4. in an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, a manifold communicating with the outlet, an elongated annular diffuser communicating at one end thereof with the manifold and including a plurality of openings communicating the diffuser with an inflatable occupant restraint cushion, variable area orifice means within the manifold, means for increasing the efiective orifice area of the variable orifice means as a function of time after rupture of the seal, a tubular diffuser screen including a plurality of layers of mesh material located within the diffuser and positioned across the openings thereof to provide a tortuous pressure fluid flow path through such openings, one end of the diffuser screen opening to the one end of the difiuser, and a resilient plug closing the other end of the diffuser screen. 

1. In an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, a manifold communicating with the outlet, an elongated annular diffuser communicating at one end thereof with the manifold and including a plurality of openings communicating the diffuser with an inflatable occupant restraint cushion, variable area orifice means within the manifold, means for increasing the effective orifice area of the variable orifice means as a function of time after rupture of the seal, a layer of porous material positioned across the openings of the diffuser, and resilient means within the diffuser engageable by the pressure fluid flow adjacent the other end thereof.
 2. In an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, a manifold communicating with the outlet, an elongated annular diffuser communicating at one end thereof with the manifold and including a plurality of axially spaced circumferentially extending openings communicating the diffuser with an inflatable occupant restraint cushion, variable area orifice means within the manifold, means for increasing the effective orifice area of the variable orifice means as a function of time after rupture of the seal, means within the diffuser providing an elongated layer of porous material covering the openings of the diffuser, and resilient means within the diffuser engageable by the pressure fluid flow downstream of the openings.
 3. In an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, passage means communicating the outlet with an elongated hollow diffuser, variable area orifice means within the passage means receiving pressure fluid flowing through the outlet, means for increasing the effective orifice area of the variable orifice means as a function of time after rupture of the seal, means communicating the interior of the diffuser with an inflatable occupant restraint cushion and providing a tortuous pressure fluid flow path thereto, and resilient means within the diffuser engageable by the pressure fluid flow downstream of the communicating means.
 4. In an occupant restraint system, the combination comprising, a vessel providing a source of pressure fluid and having an outlet sealed by a rupturable seal, a manifold communicating with the outlet, an elongated annular diffuser communicating at one end thereof with the manifold and including a plurality of openings communicating the diffuser with an inflatable occupant restraint cushion, variable area orifice means within the manifold, means for increasing the effective orifice area of the variable orifice means as a function of time after rupture of the seal, a tubular diffuser screen including a plurality of layers of mesh material located within the diffuser and positioned across the openings thereof to provide a tortuous pressure fluid flow path through such openings, one end of the diffuser screen opening to the one end of the diffuser, and a resilient plug closing the other end of the diffuser screen. 